A color diffusion transfer photographic process has heretofore been well known using an azo dye forming compound which produces an azo dye having a diffusibility different from that of the dye forming compound as a result of development under a basic condition.
Examples of such a dye forming compound for releasing a cyan dye include those described in U.S. Pat. Nos. 3,942,987, 4,013,635, 4,273,708 and 4,268,625.
However, the compounds as described in these references have been found to have the disadvantage that they contain a nitro group in the para-position of the azo group which is subject to reduction during development that will cause discoloration. It has been also found that azo dyes containing a nitro group are generally subject to reduction by light which gives a poor fastness of image to light.
Furthermore, if these dye forming compounds are incorporated in the same layer as a light-sensitive silver halide emulsion, a phenomenon in which the development of silver halide is inhibited is often observed. Nitro groups probably cause such a phenomenon.
Examples of a cyan azo forming compound containing a trifluoromethanesulfonyl group in the prat-position of the azo group are described in Japanese Patent Application (OPI) No. 66227/78 (the term "OPI" as used herein means an "unexamined published application"). However, such compounds are disadvantageous in that the incorporation of fluorine cannot be easily accomplished and their fluorine-containing composition causes pollution. Furthermore, these compounds leave such to be desired in color sharpness and diffusion of released dye. Examples of magenta azo dye forming compounds comprising a diazo component containing a plurality of alkylsulfonyl groups are disclosed in British Patent 1,490,248 and Japanese Patent Application (OPI) No. 40402/80. However, since these compounds have a naphthol 2-position which is unsubstituted or has an electrophilic group introduced, their color hue is in too short a wavelength range. Thus, these compounds cannot be used as cyan dye forming compounds.
Therefore, cyan dye forming compounds have heretofore never been known containing a nitro group or trifluoromethanesulfonyl group in the para-position of the azo group.
Recently, novel cyan azo dye forming compounds obtained by an azo coupling of a diazo component free of nitro groups or a trifluoromethanesulfonyl group with 2-acylamino-1-naphthols have been proposed in U.S. Pat. No. 4,556,632. The dye forming compounds as described in these references are useful as cyan dyes as compared to the prior art compounds. However, these compounds have a shallow hue and thus have an insufficient color reproducibility since these compounds have a cyano group, an alkylsulfonyl group, or an arylsulfonyl group at the 2-position (relating to the azo group) of the phenyl group of the diazo component. Furthermore, since their color is shallow, they need to be used in an excess amount in order to obtain an excellent grey balance.